From c3211ae093751fe1e144a96768dcb12af1a3a613 Mon Sep 17 00:00:00 2001 From: Matt Turner Date: Mon, 1 Aug 2016 12:18:45 -0700 Subject: [PATCH] i965: Disable the unlit centroid workaround on Gen7. Once upon a time (commit 8313f44409) Paul added code for the unlit centroid workaround (WaCopyUnlitCentroidBarys). His commit message claims it fixed the EXT_framebuffer_multisample/interpolation {2,4} {centroid-deriv,centroid-deriv-disabled} piglit tests but does not say on which platform, though he cites the IVB PRM. "3DSTATE_WM [DevIVB, DevHSW]" says "[DevIVB]: Workaround: When Centroid Barycentric mode is required, HW may produce incorrect interpolation results when a 2X2 pixels have unlit pixels." I later disabled it for Haswell (commit f6db414f3c) with no known ill effects. The Sandybridge page does not have this text, but the workarounds database (see WaCopyUnlitCentroidBarys) says the issues applies *only* to Sandybridge, and in fact in commit 1a2de7dce8fc I note that disabling the workaround on Sandybridge causes the tests Paul originally mentioned to fail. So this is, and always has been, a huge confusing mess. Disabling the workaround indeed causes the tests Paul originally mentioned to fail on Sandybridge but not on Ivybridge/Baytrail. On Ivybridge: total instructions in shared programs: 6914901 -> 6909599 (-0.08%) instructions in affected programs: 106766 -> 101464 (-4.97%) helped: 884 total cycles in shared programs: 70874764 -> 70813774 (-0.09%) cycles in affected programs: 794144 -> 733154 (-7.68%) helped: 688 HURT: 186 LOST: 1 GAINED: 6 Reviewed-by: Kenneth Graunke --- src/mesa/drivers/dri/i965/brw_device_info.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/src/mesa/drivers/dri/i965/brw_device_info.c b/src/mesa/drivers/dri/i965/brw_device_info.c index 77bbe785580..56209771535 100644 --- a/src/mesa/drivers/dri/i965/brw_device_info.c +++ b/src/mesa/drivers/dri/i965/brw_device_info.c @@ -116,7 +116,6 @@ static const struct brw_device_info brw_device_info_snb_gt2 = { static const struct brw_device_info brw_device_info_ivb_gt1 = { GEN7_FEATURES, .is_ivybridge = true, .gt = 1, - .needs_unlit_centroid_workaround = true, .num_slices = 1, .max_vs_threads = 36, .max_hs_threads = 36, @@ -137,7 +136,6 @@ static const struct brw_device_info brw_device_info_ivb_gt1 = { static const struct brw_device_info brw_device_info_ivb_gt2 = { GEN7_FEATURES, .is_ivybridge = true, .gt = 2, - .needs_unlit_centroid_workaround = true, .num_slices = 1, .max_vs_threads = 128, .max_hs_threads = 128, @@ -158,7 +156,6 @@ static const struct brw_device_info brw_device_info_ivb_gt2 = { static const struct brw_device_info brw_device_info_byt = { GEN7_FEATURES, .is_baytrail = true, .gt = 1, - .needs_unlit_centroid_workaround = true, .num_slices = 1, .has_llc = false, .max_vs_threads = 36,